also, many motherboard manufacturers actually perform at a slightly higher clock rate than what is listed in the bios. my ep-8rda3+ comes from the factory ~0.9mhz FSB faster than what the bios shows. at the 11x cpu multiplier i run, that comes out to about 10mhz, and coupled with it slightly varying i watch it in CPU-Z, its enough to throw it off somewhat. you can find this referred to in some motherboard roundups here on anandtech. i've heard that mostly it's just to make a motherboard slightly faster in benchmarking, when compared to non-overclocked boards.